I can think of no reason other than a corrupt install to uninstall and install. Gene is right, but basically if you open AC on a computer which is on a network, it will look for the database on the local computer first. You will get the window which allows you to browse to the database. You would, of course, browse to the main computer and click on the xml file which would then connect you.
At times, especially the first time, you may have to right click on the AC executable file and run as administrator, which is silly but, nonetheless, required.
